1. Field of the Invention
The present invention relates to the field of molecular biology, and, more particularly, to the fields of recombinant genetics and genetic engineering. The invention further relates to DNA sequences, derived from Lactococcus lactis, which are useful as promoters and promoter/secretion promoting signals for heterologous or homologous expression in bacteria. In another aspect, the invention relates to vectors, such as plasmics, comprising the sequences of the present invention, and to host cells transformed with such vectors. Yet additional aspects of the present invention are related to methods for producing desired heterologous or homologous peptides or proteins employing the sequences, vectors, or transformed hosts of the invention. By means of the invention, greatly improved heterologous and homologous expression and secretion may be achieved.
2. Description of Related Art
The lactic acid bacteria are of great commercial importance for, among other things, their ability to carry out fermentation, a process in which organic compounds serve as both electron donors and electron acceptors. Lactic fermentation reduces pyruvate to lactate in a single step reaction catalyzed by NAD-linked lactic dehydrogenase, without gas formation, and is the first stage in cheese manufacture. Thus, lactic fermentations are responsible for souring, or acidification, of milk and certain other foods, which allows for anaerobic preservation. Further, these processes are involved in the formation of interesting and desirable food and beverage flavors.
The lactic acid bacteria are thus of significant commercial importance. To-date, however, much of the work involving recombinant genetics has been carried out in other bacteria, such as E. coli. One result of this is that the genetics of the lactic acid bacteria are relatively less well understood or characterized. Inasmuch as there is a great deal of practical knowledge relating to the cultivation of lactic acid bacteria for commercial purposes, a continuing need exists for the application of recombinant genetic techniques to the understanding of these bacteria.